1. Field of the Disclosure
The present disclosure relates to an electric power supply system for a vehicle.
2. Description of Related Art
As an electric power supply system for a vehicle which supplies electric power to various electric loads (headlamp, air conditioner, audio, meter electric components, wiper, and the like) mounted in a vehicle, an electric power supply system for a vehicle in which two batteries are connected in parallel is known. In the electric power supply system for a vehicle, the two batteries connected in parallel are charged with electric power supplied from an alternator (in a hybrid vehicle or the like, a direct current to direct current converter). In the electric power supply system for a vehicle, in a case where a high load is applied to a first battery (for example, a lead battery) by operation of various electric loads, the supply of electric power is also performed from a second battery (for example, a nickel-hydrogen battery), whereby appropriate electric power is supplied to various electric loads. With this, it is possible to stabilize the supply of electric power to various electric loads.
Here, in the electric power supply system for a vehicle, a method of calculating internal resistance of the second battery is examined. In general, as a method of calculating internal resistance of a battery, for example, a method using voltage fluctuation and current fluctuation due to discharging of the battery at the time of electric load operation is exemplified (see Japanese Patent Application Publication No. 2012-132726 (JP 2012-132726 A) described below). According to the method using voltage fluctuation and current fluctuation at the time of electric load operation in this way, since a dedicated discharging circuit or the like is not required, it is advantageous in that it is possible to calculate the internal resistance of the battery at low cost.